title: Influence of relative humidity on the nanoscopic topography and dielectric constant of thin films of PPy:PSS.
abstract: The morphological, electric, and dielectric properties of water-based conjugated polymer blends, such as polypyrrole:polystyrene sulfonate (PPy:PSS) or poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), are known to be influenced by the water content. These properties also influence the macroscopic performance when the conjugated polymer blends are employed in a device. An in situ humidity-dependence study on thin films of PPy:PSS by Kelvin probe force microscopy (KPFM) is presented. A particular KPFM mode, dielectric imaging, is used, which detects the second harmonic electrostatic force. Thin PPy:PSS films are drop-coated on hydrophobic graphite substrates. Upon increasing the relative humidity, the hydrophilic PSS is swelled and dewetted on the substrate, while the hydrophobic PPy remains almost unchanged. The swelling and dewetting of PSS results in irreversible morphological changes in the thin films, as well as nanoscopic rearrangement on the surface of the PPy:PSS films. The nanoscopic rearrangement can only be detected by dielectric imaging. It is also observed that relative humidity affects unannealed and thermally annealed PPy:PSS thin films differently.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55118 Mainz, Germany.
authors.forename: Ling
authors.initials: L
authors.lastname: Sun
authors.forename: Jianjun
authors.initials: J
authors.lastname: Wang
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.forename: Elmar
authors.initials: E
authors.lastname: Bonaccurso
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry; D004553:Electric Conductivity; D006108:Graphite / Q000737:chemistry; D006813:Humidity; D057927:Hydrophobic and Hydrophilic Interactions; D049329:Nanostructures / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry; D013499:Surface Properties
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D011108:Polymers; D011137:Polystyrenes; D011758:Pyrroles; C121383:poly(3,4-ethylene dioxythiophene); C067635:polypyrrole; C003321:polystyrene sulfonic acid; D006108:Graphite